The objective for the period of the proposed work is to generally improve our understanding and practice of using scanning tunneling microscopes (STMs) to study organic molecules, and of tunneling spectroscopy methods and DNA molecules in particular. The work will be done with STMs built by the principal investigator that have already imaged DNA adsorbed on graphite in air at room temperature. The proposed work will be done both in air at room temperature and in vacuum at cryogenic temperatures. Other molecules to be studied include liquid crystals, porphyrins, and sorbic acid. This work will contribute to development of STMs as analytical tools for more routine use by biochemists, with the specific possibility of identifying the nucleotides in an arbitrary DNA molecule. This may permit very fast sequencing of DNA with extremely small samples. Although many solid state surfaces have been extensively studied experimentally with STMs and theoretically modeled, very few molecules have been studied and molecular models for understanding STM data have not been developed. Images of DNA with its primary helix resolved were first reported only the year before last (1988). Very little molecular spectroscopy has been reported, none on DNA. The proposed research will help open the new, very promising field of molecular studies with STMs.